1. Field of the Invention
This invention relates to staged-combustion rocket engines and espcially to a pre-regenerated, staged-combustion rocket engine utilizing a heat exchanger to raise the temperature of the fluid operating the low-pressure turbines.
2. Description of the Prior Art
Staged-combustion rocket cycles wherein all propellants are burned at high pressure become pressure-limited for non-cooled turbine designs because of a limited fuel flow available for turbine drive. In current staged-combustion designs, such as the space shuttle main engine (SSME), the entire fuel flow, other than that used for chamber-jacket cooling, is used to drive the turbine pump power units. Any reduction of the flow of the fuel (or oxidizer) used as a coolant in the combustion-chamber cooling jacket, the coolant fuel then being sent through the low-pressure turbopumps, is generally unfeasible because the resulting higher chamber-wall temperatures and coolant temperatures result in a reduced thermal margin and thermal life characteristic of the chamber walls. Additional oxidizer flow to the preburner(s) is available in such cycles but this causes a higher turbine blade temperature with a consequent blade and turbine life limitation problem. As a result, current technology limits typical O.sub.2 --H.sub.2 staged-combustion cycles to about 3500 psia combustion-chamber pressure.